so what causes this?

[DanCope]

I've been following this thread with some interest and have been doing a little digging on the web. The general opinion seems to be that it's a mechanical problem and, as has been mentioned here, one that can be somewhat improved by slowing down travel speeds and tweaking the accel/jerk parameters.

It also seems to me that this problem is specific to Cartesian coordinate systems. I haven't yet found any complaints about "ringing" on delta type machines. Can anyone confirm that delta machines are immune to this ringing problem?

I think you are right, I have also found more information about stepper motors in general now that I had a better idea of what to look for. The 'Vibration Problem' section on this page seems to describe the problem we have. It kind of seems it's just a limitation of these motors.

I imagine delta printers don't show this issue because of the way it drives the motors. It is probably less likely to bring a motor to a sudden stop and any vibration would be absorbed differently into a print than straight across an axis.

The acceleration settings apply to both the acceleration and deceleration phases of a movement.

That makes sense. I would guess there is a lower limit to how slow it could go before it stops the motor completely so even decelerating slower might not help in terms of a sudden stop.